C-peptide (Serum/Plasma) Concentration, 15-Minute Postprandial

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of diabetes, such as frequent urination, excessive thirst, or unexplained weight changes. It may also be used to monitor how well your pancreas is working in people with known diabetes or other conditions affecting insulin production.

What to Expect Before the Test

You’ll fast for about 12 hours before the test, but you can drink water. On the day of the test, you’ll eat a standard meal, and blood will be drawn 15 minutes afterward. The test is quick and usually done in a clinic or lab.

What the Test Results Mean

C-peptide levels help determine if your body produces insulin independently. Low levels may indicate insufficient pancreatic function, while normal or high levels suggest adequate production. This test is not used to diagnose diabetes directly but supports broader health assessments.

Common Conditions Monitored

This test is often used in people with type 1 diabetes to check for residual pancreatic function or in type 2 diabetes to assess insulin secretion patterns. It may also be part of evaluations for pancreatic diseases or autoimmune conditions affecting insulin production.